Selecting COBOL perform statements for inlining

ABSTRACT

An approach to selecting statements for inlining in a COBOL program involving creating a PERFORM Graph (PG), determining whether the PG is a Directed Acyclic Graph (DAG), responsive to determining the PG is not a DAG, identifying a maximum sub-graph DAG corresponding to the PG, computing one or more infeasible paths associated with a Control Flow Graph (CFG), wherein the infeasible paths are induced by PERFORM range calls associated with a plurality of edges corresponding to the PG or the maximum sub-graph DAG, ordering the plurality of edges corresponding to the PG or the maximum sub-graph DAG in a list, selecting one or more edges, based on traversing the list of the plurality of edges and generating an indicator of the one or more selected edges.

BACKGROUND

The present invention relates generally to the field of CommonBusiness-Oriented Language (COBOL), and more particularly to inlining.

COBOL is a computer programming language designed for business-orientedapplication use. COBOL utilizes an English-language based syntax withwhich a programmer can write program instructions. For example, PERFORMis a statement used in COBOL to indicate an action to be executed. APERFORM range refers to the sequence of code, i.e., the subroutine,which is called by a PERFORM statement. In computer programming,inlining refers to a manual or compiler optimization technique where thebody of a called function replaces the call site in a calling statementand/or function. In COBOL, PERFORM ranges can be inlined so that acalled PERFORM range can replace the call site in another callingPERFORM statement, for example.

SUMMARY

As disclosed herein, a computer system for selecting statements toinline in a COBOL program, the computer system comprising: one or morecomputer processors; one or more computer readable storage media;program instructions stored on the one or more computer readable storagemedia for execution by at least one of the one or more processors, theprogram instructions comprising: program instructions to create, by aperform identifier, a PERFORM Graph (PG) based on a received COBOLprogram; program instructions to determine, by the perform identifier,whether the PG is a Directed Acyclic Graph (DAG); responsive todetermining the PG is not a DAG, program instructions to identify, bythe perform identifier, a maximum sub-graph DAG corresponding to the PG;program instructions to compute, by the perform identifier, one or moreinfeasible paths associated with a Control Flow Graph (CFG) wherein theone or more infeasible paths are induced by PERFORM range callsassociated with a plurality of edges corresponding to the PG or themaximum sub-graph DAG; program instructions to order, by the performidentifier, the plurality of edges corresponding to the PG or themaximum sub-graph DAG in a list wherein the plurality of edges areordered from a highest to a lowest number of the one or more infeasiblepaths induced; program instructions to select, by the performidentifier, one or more edges based on traversing the list of theplurality of edges wherein a preconfigured threshold limits selection ofa maximum number of the one or more edges; program instructions togenerate, by the perform identifier, an indicator of the one or moreedges selected; responsive to determining the PG is a DAG or identifyingthe maximum sub-graph DAG, program instructions to compute, by theperform identifier, for a plurality of nodes comprising the PG or themaximum sub-graph DAG, a number of distinct paths from a root node toeach of the plurality of nodes and wherein the plurality of nodescomprising the PG or the maximum sub-graph DAG correspond to PERFORMranges comprising the COBOL program and the plurality of nodes includethe root node which corresponds to a main program code sequence andwherein a number of the one or more infeasible paths associated with anedge (F,T) is computed based on the following formula: F_(num) _(_)_(paths)*(T_(num) _(_) _(paths)−F_(num) _(_) _(paths)); and programinstructions to send, by the perform identifier, the indicator of theone or more edges selected to a compiler for inlining the PERFORM rangesassociated with the one or more edges selected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating a distributed dataprocessing environment, in accordance with an embodiment of the presentinvention;

FIG. 2 is a flowchart depicting operational steps of a PERFORMidentifier on a computer system within the data processing environmentof FIG. 1, in accordance with an embodiment of the present invention;

FIGS. 3A-B depict an example segment of a COBOL program and a PERFORMgraph corresponding to the example segment of a COBOL program,respectively, in accordance with an embodiment of the present invention;and

FIG. 4 is a block diagram of components of the computer system executingthe PERFORM identifier, in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

Modeling the flow of PERFORM statements in a Control Flow Graph (CFG)can lead to a complex CFG with infeasible paths. A CFG is a graphicalrepresentation depicting the logical flow of executed statements (e.g.,assignment statements, PERFORM statements, etc.) taken by a program.CFGs are often used for data flow analysis and compiler optimizations.Embodiments of the present invention recognize that inlining COBOLPERFORM ranges can improve a CFG by reducing the number of infeasiblepaths associated with the CFG. Therefore, a solution is provided hereinfor identifying PERFORM ranges in a COBOL program to be inlined with theuse of a PERFORM Graph (PG).

A PG is a form of a directed graph which depicts the directional flow ofcalls to PERFORM ranges in a COBOL program. The nodes comprising a PGrepresent PERFORM ranges corresponding to the COBOL program. The edgesin a PG, indicating a directional flow between the nodes, representdirect calls to PERFORM ranges from calling PERFORM ranges. Embodimentsof the present invention provide a solution wherein an analysis of a PGcorresponding to a COBOL program is performed for determining PERFORMranges to be inlined. This is done to reduce the complexity, e.g.,reduce the number of infeasible paths, involved with a CFG associatedwith the COBOL program.

As an example of an “infeasible path” as the term is used herein, ifthere are two calls to the same called PERFORM range from a first and asecond calling PERFORM range, there is an apparent path (in anassociated CFG) from the second calling PERFORM range through the calledPERFORM range and back to the first calling PERFORM range. This apparentpath, however, cannot be traversed during execution for any input givento the associated COBOL program, hence this apparent path is infeasible.

In describing embodiments in detail with reference to the figures, itshould be noted that references in the specification to “an embodiment,”“other embodiments,” etc., indicate that the embodiment described mayinclude a particular feature, structure, or characteristic, but everyembodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, describing a particularfeature, structure or characteristic in connection with an embodiment,one skilled in the art has the knowledge to affect such feature,structure or characteristic in connection with other embodiments whetheror not explicitly described.

The present invention will now be described in detail with reference tothe figures. FIG. 1 is a functional block diagram illustrating adistributed data processing environment 100, in accordance with oneembodiment of the present invention.

Distributed data processing environment 100 comprises computer system102 and communication device 150, interconnected over network 140.Computer system 102 can be a laptop computer, tablet computer, netbookcomputer, personal computer (PC), a desktop computer, a personal digitalassistant (PDA), a smart phone, or any programmable electronic devicecapable of communicating with communication device 150 via network 140.Computer system 102 comprises COBOL 104 with compiler 106 fortransforming source code written in COBOL 104 into an executableprogram.

Computer system 102 may include internal and external hardwarecomponents, as depicted and described in further detail with respect toFIG. 4.

According to one embodiment of the present invention, compiler 106further comprises PERFORM identifier 108 which is a program foridentifying PERFORM statements and/or ranges in a COBOL program to beinlined. PERFORM identifier 108 further comprises graph creator 109,path computer 110, graph maximizer 111 and edge selector 112. Graphcreator 109 is a component for creating a PG corresponding to a COBOLprogram. Path computer 110 is a component for computing the numbers ofinfeasible paths that the PERFORM range calls, corresponding to edges ina PG, are responsible for inducing. Graph maximizer 111 is a componentfor determining whether a PG is a directed acyclic graph (DAG). If graphmaximizer 111 determines that a PG is not a DAG, graph maximizer 111 canidentify the maximum sub-graph corresponding to the PG that is a DAG.Edge selector 112 is a component which selects one or more edges in thePG based on the computed infeasible paths and can generate an indicatorwhich indicates the one or more selected edges.

In various embodiments of the present invention, communication device150 can be a laptop computer, tablet computer, netbook computer,personal computer (PC), a desktop computer, a personal digital assistant(PDA), a smart phone, or any programmable electronic device capable ofcommunicating with computer system 102 via network 140.

Network 140 can be, for example, a local area network (LAN), a wide areanetwork (WAN) such as the Internet, or a combination of the two, and caninclude wired, wireless, or fiber optic connections. In general, network140 can be any combination of connections and protocols that willsupport communications between computer system 102 and communicationdevice 150.

FIG. 2 is a flowchart 200 depicting operational steps of PERFORMidentifier 108, in accordance with an embodiment of the presentinvention. The illustrative example of FIG. 2 is provided to facilitatediscussion of aspects of the present invention, and it should beappreciated that FIG. 2 provides only an illustration of an embodimentof the present invention and does not imply any limitations with regardto the variations or configurations in which different embodiments maybe implemented.

Graph creator 109 creates a PG associated with a program in COBOL 104(step 202). The PG is a directed graph comprising a plurality of nodescorresponding to PERFORM ranges in the COBOL program. Graph creator 109creates a root node in the PG which represents the main program whereexecution begins. The PG further comprises edges which illustrate thelogical directional flow of the nodes (corresponding to the PERFORMranges) as the COBOL program is being executed. An example of a PGcreated by graph creator 109, according to one embodiment of the presentinvention, will be depicted and described in further detail with respectto FIG. 3B.

Graph maximizer 111 determines if the PG is a DAG (decision block 204).A DAG as the term is used herein refers to a directed graph having atopological ordering with no directed cycles, i.e., there are nosequences of directed edges starting from a node N that cycle back tonode N. Graph maximizer 111 can determine if the PG is a DAG using knownalgorithms, e.g., Tarjan's strongly connected components algorithm, orother techniques apparent to one of ordinary skill in the art.Responsive to determining that the PG is not a DAG (step 204, NObranch), graph maximizer 111 identifies a maximum sub-graph (comprisingthe PG) which is a DAG (step 206). For example, graph maximizer 111 canuse an algorithm apparent to one of ordinary skill in the art toidentify a maximum sub-graph DAG.

Responsive to a determination that the PG is a DAG (step 204, YESbranch) or an identification of the maximum sub-graph DAG, path computer110 computes a number of distinct paths from the root node to each nodecomprising the PG (step 208). For a given node N, the number of distinctpaths leading from the root node to node N is denoted herein as N_(num)_(_) _(paths). This parameter represents the number of distinct paths inthe PG or maximum sub-graph DAG, e.g., paths through other nodes, thatthe program takes to get to node N from the root node, representing themain program code sequence. The distinct paths through the PG or maximumsub-graph DAG represent paths of PERFORM range calls leading to aneventual call of the PERFORM range representing the given node N.

Path computer 110 computes the number of infeasible paths, associatedwith a CFG corresponding to the COBOL program, that each edge comprisingthe PG or maximum sub-graph DAG is inducing (step 210). In this context,edges depict a directed logical flow between adjacent nodes,representing a direct call from one PERFORM range to another. The numberof distinct paths for a given node N, i.e., N_(num) _(_) _(paths), maycomprise one or more edges of the PG or maximum sub-graph DAG, forexample. For a given edge (F,T) in the PG or maximum sub-graph DAG(representing an edge starting at a node F and ending at a node T), thefollowing formula is used by path computer 110 to compute the number ofinfeasible paths the edge is inducing:F_(num) _(_) _(paths)*(T_(num) _(_) _(paths)−F_(num) _(_) _(paths))

The value resulting from this formula for a given edge (F,T) is anapproximate number of infeasible paths (associated with the CFG) whichthe edge (F,T) is responsible for inducing. Path computer 110 computes avalue with this formula for each edge comprising the PG or maximumsub-graph DAG. In other embodiments of the present invention, otherformulas and/or algorithms apparent to one of ordinary skill in the artcan be used to compute a number of infeasible paths that an edge isinducing in a CFG.

Edge selector 112, using the values computed by path computer 110,orders the edges associated with the PG or maximum sub-graph DAG in alist (step 212). For example, edge selector 112 orders the edges fromthe highest to lowest numbers of infeasible paths that the edges areinducing. Edge selector 112 traverses the ordered list of edgesassociated with the PG or maximum sub-graph DAG to select edges to beinlined (step 214). In the embodiment where edges are ordered from thehighest to lowest numbers of infeasible paths, edge selector 112traverses the ordered list from top to bottom. The highest edge in thelist represents a PERFORM range call inducing a greatest number ofinfeasible paths associated with the CFG, therefore edge selector 112can select the highest edge for inlining a PERFORM range associated withthe highest edge. Edge selector 112 can continue to traverse the listfor selecting edges up to a preconfigured limit.

Edge selector 112 can have a preconfigured “budget” representing amaximum number of edges that can be selected for PERFORM range inlining.For example, once edge selector 112 has selected the maximum number ofedges prescribed by the budget, edge selector 112 can discontinuetraversing the ordered list of edges. Additionally or alternatively,edge selector 112 can be preconfigured to only select edges exceeding aminimum threshold number of infeasible edges they are responsible forinducing.

Edge selector 112 generates an indicator associated with the selectededges and sends the indicator to compiler 106 (step 216). The indicatorprovides an indication of which PERFORM ranges and/or statements,associated with the selected edges, can be inlined in the COBOL program.For example, inlining a PERFORM range associated with a selected edgecan comprise replacing, in a first PERFORM range, a call to a secondPERFORM range with the body of the second PERFORM range. This PERFORMrange inlining removes edges in the CFG, thereby reducing the number ofinfeasible paths (and therefore, the complexity) associated with the CFGcorresponding to the COBOL program.

FIG. 3A depicts a segment 300 of an example COBOL program, in accordancewith an embodiment of the present invention. Statements such as “PERFORMA” and “PERFORM B” in main program 302 are examples of PERFORMstatements. As an example of a PERFORM range call, “PERFORM A”represents a call to PERFORM range 304, comprising “PERFORM C” and“PERFORM D.” PERFORM range 306 comprises “PERFORM C” and “PERFORM D”,PERFORM range 308 comprises “PERFORM D” and PERFORM range 310 comprises“EXIT.”

FIG. 3B is an illustration of an example PG 350 corresponding to thesegment of the example COBOL program depicted in FIG. 3A, in accordancewith an embodiment of the present invention. PG 350 is a DAG comprisingnodes MAIN, A, B, C and D, and edges indicated by arrows between thenodes. MAIN, i.e., the root node, corresponds to main program 302associated with the COBOL program of FIG. 3A and nodes A-D representPERFORM ranges comprising the COBOL program. The edges represent directcalls to the PERFORM ranges corresponding to nodes A-D. The numbers onthe nodes in PG 350 correspond to the value N_(num) _(_) _(paths)associated with each node, computed by path computer 110.

For example, in PG 350 there are four distinct paths from MAIN to nodeD. The four distinct paths from MAIN to node D through a sequence ofedges are as follows: {MAIN, A, D}; {MAIN, A, C, D}; {MAIN, B, D} and{MAIN, B, C, D}. The number of infeasible paths induced by an edge (inan associated CFG) is computed by path computer 110 for each edge in PG350, as previously described. Using the formula F_(num) _(_)_(paths)*(T_(num) _(_) _(paths)−F_(num) _(_) _(paths)), the number ofinfeasible paths for each edge in PG 350 are as follows: (MAIN,A):0,(MAIN,B):0, (A,D):3, (A,C):1, (B,C):1, (B,D):3, (C,D):4.

In a list of edges associated with PG 350, ordered from the highest tolowest numbers of infeasible paths induced, edge (C,D) would appear atthe top. Therefore, edge (C,D) would be the first edge selected by edgeselector 112. Edge selector 112 can continue to traverse the orderedlist, selecting other edges for PERFORM range inlining up to apreconfigured threshold limit. When edge selector 112 has completedselecting edges, an indicator indicating the selected edges, e.g., edge(C,D), is generated and sent to compiler 106 for inlining associatedPERFORM ranges and/or statements.

FIG. 4 depicts a block diagram 400 of components of computer system 102in accordance with an illustrative embodiment of the present invention.It should be appreciated that FIG. 4 provides only an illustration ofone implementation and does not imply any limitations with regard to theenvironments in which different embodiments may be implemented. Manymodifications to the depicted environment may be made.

Computer system 102 includes communications fabric 402, which providescommunications between cache 416, memory 406, persistent storage 408,communications unit 410, and input/output (I/O) interface(s) 412.Communications fabric 402 can be implemented with any architecturedesigned for passing data and/or control information between processors(such as microprocessors, communications and network processors, etc.),system memory, peripheral devices, and any other hardware componentswithin a system. For example, communications fabric 402 can beimplemented with one or more buses or a crossbar switch.

Memory 406 and persistent storage 408 are computer readable storagemedia. In this embodiment, memory 406 includes random access memory(RAM). In general, memory 406 can include any suitable volatile ornon-volatile computer readable storage media. Cache 416 is a fast memorythat enhances the performance of computer processor(s) 404 by holdingrecently accessed data, and data near accessed data, from memory 406.

PERFORM identifier 108 can be stored in persistent storage 408 and inmemory 406 for execution by one or more of the respective computerprocessors 404 via cache 416. In an embodiment, persistent storage 408includes a magnetic hard disk drive. Alternatively, or in addition to amagnetic hard disk drive, persistent storage 408 can include a solidstate hard drive, a semiconductor storage device, read-only memory(ROM), erasable programmable read-only memory (EPROM), flash memory, orany other computer readable storage media that is capable of storingprogram instructions or digital information.

The media used by persistent storage 408 can also be removable. Forexample, a removable hard drive can be used for persistent storage 408.Other examples include optical and magnetic disks, thumb drives, andsmart cards that are inserted into a drive for transfer onto anothercomputer readable storage medium that is also part of persistent storage408.

Communications unit 410, in these examples, provides for communicationswith other data processing systems or devices. In these examples,communications unit 410 includes one or more network interface cards.Communications unit 410 can provide communications through the use ofeither or both physical and wireless communications links. PERFORMidentifier 108 can be downloaded to persistent storage 408 throughcommunications unit 410.

I/O interface(s) 412 allows for input and output of data with otherdevices that can be connected to computer system 102. For example, I/Ointerface 412 can provide a connection to external devices 418 such as akeyboard, keypad, a touch screen, and/or some other suitable inputdevice. External devices 418 can also include portable computer readablestorage media such as, for example, thumb drives, portable optical ormagnetic disks, and memory cards. Software and data used to practiceembodiments of the present invention, e.g., PERFORM identifier 108, canbe stored on such portable computer readable storage media and can beloaded onto persistent storage 408 via I/O interface(s) 412. I/Ointerface(s) 412 also connect to a display 420. Display 420 provides amechanism to display data to a user and can be, for example, a computermonitor.

The programs described herein are identified based upon the applicationfor which they are implemented in a specific embodiment of theinvention. However, it should be appreciated that any particular programnomenclature herein is used merely for convenience, and thus theinvention should not be limited to use solely in any specificapplication identified and/or implied by such nomenclature.

The present invention can be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product can include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium can be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network can comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention can be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions can execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer can be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions can be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionscan also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions can also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block can occur out of theorder noted in the figures. For example, two blocks shown in successioncan, in fact, be executed substantially concurrently, or the blocks cansometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The terminology used herein was chosen to best explain the principles ofthe embodiment, the practical application or technical improvement overtechnologies found in the marketplace, or to enable others of ordinaryskill in the art to understand the embodiments disclosed herein.

What is claimed is:
 1. A computer system for selecting statements toinline in a COBOL program, the computer system comprising: one or morecomputer processors; one or more computer readable storage media;program instructions stored on the one or more computer readable storagemedia for execution by at least one of the one or more processors, theprogram instructions comprising: program instructions to create, by aperform identifier, a PERFORM Graph (PG) based on a received COBOLprogram; program instructions to determine, by the perform identifier,whether the PG is a Directed Acyclic Graph (DAG); responsive todetermining the PG is not a DAG, program instructions to identify, bythe perform identifier, a maximum sub-graph DAG corresponding to the PG;program instructions to compute, by the perform identifier, one or moreinfeasible paths associated with a Control Flow Graph (CFG) wherein theone or more infeasible paths are induced by PERFORM range callsassociated with a plurality of edges corresponding to the PG or themaximum sub-graph DAG; program instructions to order, by the performidentifier, the plurality of edges corresponding to the PG or themaximum sub-graph DAG in a list wherein the plurality of edges areordered from a highest to a lowest number of the one or more infeasiblepaths induced; program instructions to select, by the performidentifier, one or more edges based on traversing the list of theplurality of edges wherein a preconfigured threshold limits selection ofa maximum number of the one or more edges; program instructions togenerate, by the perform identifier, an indicator of the one or moreedges selected; responsive to determining the PG is a DAG or identifyingthe maximum sub-graph DAG, program instructions to compute, by theperform identifier, for a plurality of nodes comprising the PG or themaximum sub-graph DAG, a number of distinct paths from a root node toeach of the plurality of nodes and wherein the plurality of nodescomprising the PG or the maximum sub-graph DAG correspond to PERFORMranges comprising the COBOL program and the plurality of nodes includethe root node which corresponds to a main program code sequence andwherein a number of the one or more infeasible paths associated with anedge (F,T) is computed based on the following formula: F_(num) _(_)_(paths)*(T_(num) _(_) _(paths)−F_(num) _(_) _(paths)); and programinstructions to send, by the perform identifier, the indicator of theone or more edges selected to a compiler for inlining the PERFORM rangesassociated with the one or more edges selected.